Many telecommunication switching systems might include plurality of I/O Cards (called line cards or network interface cards) for processing different data from network interfaces like E1, DS1, STM-n, OC-n etc and send this processed data to traffic switch (Called Switch card) to switch data from one network interface to other. In such telecommunication systems the data from line cards to switch card passes over a backplane which connects various cards in a system. Such telecommunication system is called network element. In a network there is plurality of such network elements. In networks like SONET/SDH, all these network elements need to work in locked mode traceable to PRC (Primary Reference Clock). The synchronization from one network element to other is passed over various interfaces like E1, DS1, STM-n, OC-n etc.
Each network interface card extracts synchronization clocks from various network interfaces and sends them to at least one system synchronizer. These clocks are typically of order of few KHz. The system synchronizer monitors subset of these clock and selects one among them based on user defined priority and quality of the clocks. Thus system synchronizer, synchronize the network element so that the entire outgoing interfaces from the said network element are in sync.
Further in order to avoid single point of failure, it is well know method in the telecommunication systems to replicate critical sub systems like power supply, switch card, network element controller, system synchronizer etc. Further, the critical subsystems like traffic switch, system synchronizer and chassis controller are integrated into single card called controller. Such cards are replicated, one controller acting as master and one or more acting as slave controllers.
Further as the number of network interface cards increases, the number of clock that has to be passed to master and slave controllers increases. This increases the backplane interface connections making the controller and backplane design complex.
Therefore, there is a need to develop system architecture and a method to achieve effective way to pass various low frequency clocks from network interface cards to controller cards using reduced interface count